Quartz Crystal Microbalance Sensor System Research Articles

Sensing performance of Schiff base-calix[4]arene including amide units for detection of pharmaceutically active compounds on QCM sensor system

This study aimed to investigate the sensing performance of a Quartz Crystal Microbalance (QCM) sensor coated with a calix[4]arene derivative (calixarene phenol amide, CPhA), containing both Schiff base and amide groups against various pharmaceutically active compounds (PhACs) such as ibuprofen, diphenhydramine, naproxen, and ascorbic acid in aqueous media. CPhA was successfully coated on the QCM crystal surface, and its surface properties were studied using Atomic Force Microscopy (AFM) and contact angle measurements. Sensing studies showed that the CPhA-coated QCM sensor detected more PhACs than the compound 4 (unfunctionalized derivative)-coated sensor. The highest frequency variation and binding ratio values were achieved with the QCM sensor with a relatively low coating amount. The CPhA-coated QCM sensor achieved higher adsorption capacity and was significantly more sensitive to all PhACs than the compound 4-coated one. The fabricated sensor showed remarkable reproducibility for all PhACs except naproxen (NAP). The fabricated sensor exhibited a remarkable sensing performance for detecting PhACs, which is promising for developing novel calix[4]arene-coated QCM sensors for PhACs.

Non-invasive Exhaled Breath and Skin Analysis to Diagnose Lung Cancer: Study of Age Effect on Diagnostic Accuracy.

Development of simple, fast, and non-invasive tests for lung cancer diagnostics is essential for clinical practice. In this paper, exhaled breath and skin were studied as potential objects to diagnose lung cancer. The influence of age on the performance of diagnostic models was studied. Gas chromatography in combination with mass spectrometry (MS) was used to analyze the exhaled breath of 110 lung cancer patients and 212 healthy individuals of various ages. Peak area ratios of volatile organic compounds (VOCs) were used for data analysis instead of VOC peak areas. Various machine learning algorithms were applied to create diagnostic models, and their performance was compared. The best results on the test data set were achieved using artificial neural networks (ANNs): classification of patients with lung cancer and young healthy volunteers: 88 ± 4% sensitivity and 83 ± 3% specificity; classification of patients with lung cancer and old healthy individuals: 81 ± 3% sensitivity and 85 ± 1% specificity. The difference between performance of models based on young and old healthy groups was minor. The results obtained have shown that metabolic dysregulation driven by the disease biology is too high, which significantly overlaps the age effect. The influence of tumor localization and histological type on exhaled breath samples of lung cancer patients was studied. Statistically significant differences between some parameters in these samples were observed. A possibility of assessing the disease status by skin analysis in the Zakharyin-Ged zones using an electronic nose based on the quartz crystal microbalance sensor system was evaluated. Diagnostic models created using ANNs allow us to classify the skin composition of patients with lung cancer and healthy subjects of different ages with a sensitivity of 69 ± 2% and a specificity of 68 ± 8% for the young healthy group and a sensitivity of 74 ± 7% and a specificity of 66 ± 6% for the old healthy group. Primary results of skin analysis in the Zakharyin-Ged zones for the lung cancer diagnosis have shown its utility, but further investigation is required to confirm the results obtained.

GC-like Graphene-Coated Quartz Crystal Microbalance Sensor with Microcolumns.

Many research groups have been interested in the quartz crystal microbalance (QCM)-based gas sensors due to their superb sensitivity originated from direct mass sensing at the ng level. Despite such high sensitivities observed from QCM sensors, their ability to identify gas compounds still needs to be enhanced. Herein, we report a highly facile method that utilizes microcolumns integrated on a QCM gas-responsive system with enhanced chemical selectivity for sensing and ability to identify volatile organic compound single gases. Graphene oxide (GO) flakes are coated on the QCM electrode to substantially increase the adsorption of gas molecules, and periodic polydimethylsiloxane microcolumns with micrometer-scale width and height were installed on the GO-coated QCM electrode. The observed frequency shifts upon sensing of various single gas molecules (such as ethanol, acetone, hexane, etc.) can be analyzed accurately using a simple exponential model. The QCM sensor system with and without the microcolumn both exhibited high detection response values above 50 ng/cm2 for sensing of the gases. Notably, the QCM sensor equipped with the microcolumn features gas identification ability, which is observed as distinct diverging behavior of time constants upon detection of different gases caused by the difference in diffusional transfer of molecules through the microcolumns. For example, the difference in the calculated time constant between ethanol and acetone increased from 22.6 to 92.1 s after installation of the microcolumn. This approach provides an easy and efficient method for identification of single gases, and it may be applied in various advanced sensor systems to enhance their gas selectivity.

Molecularly imprinted polymer based quartz crystal microbalance sensor system for sensitive and label-free detection of synthetic cannabinoids in urine

Herein, we prepared a novel quartz crystal microbalance (QCM) sensor for synthetic cannabinoids (JWH-073, JWH-073 butanoic acid, JWH-018 and JWH-018 pentanoic acid,) detection. Firstly, the synthetic cannabinoid (SCs) imprinted (MIP) and non-imprinted (NIP) nanoparticles were synthesized by mini-emulsion polymerization system. The SCs-imprinted nanoparticles were first characterized by SEM, TEM, zeta-size and FTIR-ATR analysis and then were dropped onto the gold QCM surface. The SCs-imprinted QCM sensor was characterized by an ellipsometer, contact angle, and AFM. The limit of detection was found as 0.3, 0.45, 0.4, 0.2 pg/mL JWH-018, JWH-073, JWH-018 pentanoic acid and JWH-073 butanoic acid, respectively. The selectivity of the SCs-imprinted QCM sensor was shown by using JWH-018, JWH-018 pentanoic acid, JWH-073 and JWH-073 butanoic acid. According to the results, the SCs-imprinted QCM sensors show highly selective and sensitive in a broad range of synthetic cannabinoid concentrations (0.0005–1.0 ng/mL) in both aqueous and synthetic urine solutions.

呼気中アンモニアの即時検知を目指した水晶振動子ガスセンサシステムの開発

シリカナノ粒子（SiO2）とポリアリルアミン塩酸塩（PAH）で構成された多孔性薄膜を担持した水晶振動子（QCM）アンモニアガスセンサの開発を試みた。SiO2とPAHの静電的相互作用によって自己組織化された薄膜は，湿度に高い感度を示した。また，薄膜（5層または10層）中にポリアクリル酸（PAA）を導入することで，アンモニアガスに高感度で選択性に優れた検知膜が実現できた。 PAA導入ありなしの二種類のQCMセンサを用いることで，湿度とアンモニアガスの同時定量分析が可能であった。センサ表面でのアンモニアの吸着機構をフーリエ変換赤外線分光（FTIR）測定から明らかにした。最後に，呼気中のアンモニア検知可能性を確認するために行った模擬臨床試験から，約3 ppmの病理学的レベルのアンモニアが呼気から検知可能であることがわかった。

New approach to a practical quartz crystal microbalance sensor utilizing an inkjet printing system.

The present work demonstrates a valuable approach to developing quartz crystal microbalance (QCM) sensor units inexpensively for reliable determination of analytes. This QCM sensor unit is constructed by inkjet printing equipment utilizing background noise removal techniques. Inkjet printing equipment was chosen as an alternative to an injection pump in conventional flow-mode systems to facilitate the commercial applicability of these practical devices. The results demonstrate minimization of fluctuations from external influences, determination of antigen-antibody interactions in an inkjet deposition, and quantification of C-reactive protein in the range of 50–1000 ng(x000B7)mL−1. We thus demonstrate a marketable application of an inexpensive and easily available QCM sensor system.

Monitoring the drown-out crystallization of sodium chloride on a DNA-modified surface

The drown-out crystallization of sodium chloride is conducted on a DNA-modified quartz crystal microbalance (QCM). To investigate the crystallization behavior of NaCl on a DNA template, a thiol-modified DNA oligomer is self-assembled on a gold electrode of QCM. The resonant frequency shift and resonant resistance of the DNA-modified QCM are measured with the continuous injection of ethanol in the NaCl saturated solution, and compared with those of a bare QCM without any modification. F– R diagram is interpreted to analyze a detailed mechanism of the QCM response change for the crystallization. An atomic force microscope (AFM) technique is also used to confirm the procedure of the NaCl crystallization on the DNA template. From these results, it is found that the QCM sensor system could be applied to monitor the NaCl crystallization in the aqueous solution, and to detect a super-saturation point or degree.

Humidity detection by nanostructured ZnO: A wireless quartz crystal microbalance investigation

In this paper, we present a wireless relative humidity sensor system prototype which based on quartz crystal microbalance (QCM) coated with nanostructured ZnO as sensing element. The wireless QCM sensor system is composed of two parts: the probe based on QCM sensor and the RF receiver. The probe has two functions: to sense and display the frequency signals and to transmit the signals to the receiver. The receiver connected to the personal computer can receive and record the sensor signals. Experimental results indicate that the wireless RH sensor has quite good stability and reproducibility. The interaction distance between the probe and the receiver can be varied from 5 to 300 m. The proposed system is potential to construct the low-cost, real-time online wireless gas sensor system, which can be used to monitor the pollutants in the family and the harsh environment.